A flood barrier system in Venice, Italy has proven successful in keeping high tide water out of the streets. The system has been 17 years in the making at a cost of $7B+.
CNN:
Saturday was the first acqua alta of the season for Venice. It was also the day when, after decades of delays, controversy and corruption, the city finally trialled its long-awaited flood barriers against the tide…
The defense system is called MOSE, the Italian for Moses, a name derived from the more functional Modulo Sperimentale Elettromeccanico, meaning Experimental Electromechanical Module. It consists of 78 flood barriers installed in the seabed at the lagoon's three main entrance points.
When the high tide arrives, they can rise to form a dam, stopping the Adriatic Sea surging into the lagoon and flooding the city…
A test in poor weather conditions had been the next step for the MOSE, which is not yet completed. And on Friday, when a full moon and high winds were predicted for the following morning, the city council asked permission to raise the barriers.
The usual flood sirens rang throughout the city at around 8 a.m. Saturday, while the test started half an hour later. By 10.10, the barriers were fully raised — and while the water level rose to 132 centimeters outside the MOSE, inside the lagoon, it remained at 70 centimeters — enough to keep San Marco dry."
…Calling it a "clear success," commissioner Spitz underlined on Saturday that this is "only a fundamental step towards protecting the city and the lagoon." The project — which also involves raising pavements in the lowest areas of the city to 110 centimeters, and permanent defense walls near the flood barriers — is due to be completed December 2021, when it will be handed over to the city.
Until then, it has been agreed that from now on, the barrier will be raised each time the tide hits 130 centimeters, meaning devastating floods such as last year's should be a thing of the past (at least, in the medium term. Climate change means MOSE will not hold back the water indefinitely). However, once the city takes over, the barriers will go up earlier, at 110 centimeters.
…What it does mean, however, is that acqua alta in St Mark's Square — which floods at 90 centimeters — will continue. And indeed, on Sunday, just 24 hours after the MOSE triumph, the city's iconic piazza was calf-deep in water, with a sea level of 106 centimeters.
screengrab via Arirang News/YouTube
